This invention relates to a system for the collection and handling of trimmed scrap material as it exits from the discharge side of trimming or slitting devices used in a strip processing line. More particularly, it relates to an improved use of linear accelerator devices for propelling trimmed metal scrap material away from the path of the moving parent strip and to a final disposal station. The edges of metal strip, such as rolled aluminum alloy strip, develop cracks during the rolling process, and generally a narrow band or ribbon of metal is subsequently removed continuously as scrap from both edges of the strip in a suitable processing operation. Edge trimming and slitting equipment for multiple widths utilize circular knives on the top and bottom of the horizontally moving strip. The scrap trim generated at each edge of the moving strip has to be diverted away from the parent or moving strip for disposal. Scrap chutes have been and are normally utilized for this purpose. These chutes generally comprise mechanical guides and, in some cases, are equipped with special pneumatic handling means. The ribbons of trimmed scrap after collection are then either chopped into convenient lengths, wound on scrap winders or compacted into scrap balls. In heavier gauge applications, the scrap is sometimes cut into pieces by choppers mounted on the trimmer arbor. In such instances, the cut scrap material is then diverted through chutes to suitable conveying systems and finally disposed of.
The aforesaid handling of metal strip scrap material, such as trimmed aluminum alloy scrap of indeterminate length, poses certain problems. Since a light-gauge narrow aluminum strand has very little stiffness, it is not always possible to feed the strand reliably through mechanical chutes without jamming. Process or handling speeds are generally limited by the ability of the handling equipment to reliably divert the trimmed material away from the trimming or slitting knives without causing jams. Where scrap choppers are used, the processing speed is also limited by the type of machine employed. A rotating knife holder and a stationary anvil machine can cause the trimmed scrap material to accordion between cuts, and they are not normally suitable for very light gauge aluminum scrap handling. Double rotating knives with precise backlash adjustments have been used with a certain degree of success but the process handling speeds involved are still limited by the design and travel speeds of the knives. Scrap winders that handle continuous ribbons of metal of indeterminate length are also prone to strip breakage, which, in turn, can cause process interruptions and line shut downs.
In addition to the aforesaid problems of handling, there are noise problems caused by the equipment used, and in the case of where heavier gauge metal is trimmed, the noise levels can be excessively high and undesirable as regards the equipment operators. Heavy gauge scrap transported through metal chutes to conveyors and finally falling into scrap tubs also produces extreme noise situations. Very light metal products of aluminum, such as aluminum foil, can be pneumatically handled with-less noise, but noise problems can still occur as regards foil handling in the areas of the high pressure blowers used with the foil conveyors.
Even where the aforesaid scrap handling problem situations are to some extent avoided or corrected, further problems remain as to the final disposal of the collected scrap material. Regardless, for example, of whether the trimmed scrap material, e.g., ribbonized scrap is chopped up, wound or compacted into a ball, the scrap still has to be periodically transported from various sources within a fabrication facility to a melting operation for recycling. The volume of such scrap is high due to the low density of the package, and considerable labor costs are associated with such transportation schemes. The segregation and marshalling of edge trim scrap for melting create major difficulties at a cast house relative to floor space requirements and require good planning in order to reduce melt loss by sequenced charging into the furnaces. The handling of scrap at the furnaces, in turn, causes long charging sequences because of the low density packages involved and potential alloy mixing problems due to improper alloy identification.
The instant invention eliminates the conventional chutes, mechanical scrap chopping, winding, or balling equipment and significantly simplifies the handling of trimmed metal scrap generated in a processing line for aluminum alloys and the like by the advantageous use of linear accelerator motor components in an improved and unique fashion. Linear accelerator motors have been items such as the accelerators of U.S. Pat. No. 4,462,529 used in the past to handle the transport of various wherein tubing is conveyed; U.S. Pat. No. 4,305,334, which relates to the movement of bulk material carrying cars in a tube-like conveyor; and U.S. Pat. No. 3,616,978, which involves the conveying of tubing and bar stock sections. U.S. Pat. Nos. 396,792; 1,441,250; 2,561,377; and 3,557,598 are also representative of other uses to which linear accelerators can be put in the conveying of various products other than ribbonized scrap of indeterminate length.
Linear induction motors or accelerators have also been employed in the past in connection with the feeding of loose metal scrap to a melting furnace wherein the induction motor is incorporated in the furnace structure at the entry port of the furnace for the purpose of controlling the level of the melt and downward flow of the molten metal at such entry port as illustrated, for example in U.S. Pat. No. 4,589,637. The melting furnace of U.S. Pat. No. 4,375,885 utilizes a discharge conveyor trough for the molten metal that has a linear accelerator incorporated in its structure, while in the furnace of U.S. Pat. No. 4,487,401, molten metal is moved about and transferred by induction devices. However, such accelerators as are disclosed in the aforesaid patents are not intended or designed for use in conveying in a substantially continuous fashion an indeterminate length or ribbon of metal scrap, such as light metal scrap, away from a trimming knife station and thereafter transporting the same directly and noiselessly to a melting furnace in an efficient and economical manner.
Accordingly, it is a primary purpose of the instant invention to collect and convey in an improved fashion ribbons of indeterminate lengths of scrap metal that are recovered from trimming knives in a strip processing line, such as aluminum scrap metal, directly from the trimming knives to a collection or disposal station, such as a melting furnace.
It is a further purpose of the instant invention to provide a unique system of collection and transfer of trimmed metal scrap directly from the trimming knife station of a metal strip processing line or the like in the form of a ribbon of indeterminate length to a melting furnace while avoiding all of the normal intermediate steps of chopping, coiling or balling the ribbon, etc. and while utilizing a linear accelerator device.
It is a further object of the instant invention to provide an improved and relatively trouble-free collection and transport system using linear induction motor components for capturing and conveying continuous ribbons of trimmed edge metal scrap material directly from the trimming knives of a trimmer or slitter in a strip processing line through a closed tubular conveyor into a melting furnace in a relatively noiseless and efficient fashion.
These and other objects and purposes of the instant invention are accomplished by providing an enclosed tube or tube-like conveyor of suitable refractory material for each trimmed scrap ribbon wherein the induction motor or accelerator components are advantageously incorporated in the wall structure of such conveyor and whereby such components can act in conjunction with the enclosed scrap ribbons to move successive portions of the ribbons through their respective conveyors.
In one preferred embodiment of the invention, the magnetic field generated by the motor components causes the captured metal strip or ribbon of scrap metal to travel a short distance forward in a horizontal plane and then downward in a gradual fashion through an arc that has a generous radius to a vertical plane in its movement from a trimming station to and through the entry port of a melting furnace. This furnace is located at a level below that of the trimming knives such as below the floor of the strip processing line building in which the knives are located. The trimmed ribbon of scrap is advantageously held in the center or substantially the center of the closed conveyor or tube by the appropriate disposition of the AC windings in the conveyor and the regulation of current and its frequency relative to the width and particular gauge of the trimmed material being handled. Since the trimmed scrap does not come into contact with the walls of the tubular conveyor, no significant amount of noise is generated. At the same time, the trimmed scrap material will be propelled within the chamber formed by the tubular conveyor under the required tension and speed so as to be fully coordinated with and match the speed of the slitting or trimming operation, thereby avoiding jamming of the scrap in the tubular conveyor.
As certain portions of the trimmed scrap ribbon are continuously fed or directed into the open end of the tubular conveyor, other portions of the trimmed scrap material will have been simultaneously discharged into the top of a conventional or specially designed induction melting furnace located below the floor of the facility in which the trimming knives are located while still, of course, being in line with such knives. The induction furnace can be of a conventional coreless or channel type using high frequency and adequate power to melt the incoming scrap ribbon material at a rate that is compatible with the gauge, width, speed and cross sectional size of the ribbonized scrap material as it enters the furnace.
A molten metal heel can be advantageously maintained at all times in the furnace to maintain optimum efficiency of operation; and in a further advantageous embodiment of the invention, the molten metal, such as aluminum, in the furnace can, if desired, be continuously directed through appropriate pouring troughs into the usual aluminum metal molds commonly referred to in the trade as sow molds for solidification. In such case, the sow molds can also be carried by an indexing conveyor past the furnace whereby the conveyor is indexed each time the mold is filled to a selected weight limit all in a fashion well known in the art of casting. Further the cast sows can be automatically labelled for alloy identification and conventional mold separation, and sow stacking machinery can be added to the indexing conveyor to minimize labor, etc. Finally, the stacked metal sows can be appropriately transported to a further remelt facility, if desired.
Among the many advantages provided by the improved system of the instant invention is a substantially noiseless handling of trimmed metal scrap from trimming knives to and into a melting furnace plus limitless speeds of conveying in the case of light as well as heavy gauge materials. This, in turn, means that slitting and trimming machines in strip processing lines can be operated at their design speeds without the usual interruptions caused by the standard present-day metal scrap choppers, winders and bailers, etc. Finally, the scrap disposal problems that normally occur in the case of cut, balled, or compacted trimmed scrap aluminum or the like are greatly reduced by being able to utilize uniformly sized sows from sow molds that can be fully identified as to metal content and alloy constituents. Thereafter, the scrap now in the form of sows can be stacked and transported in high density packages directly and efficiently from the slitting operations to various recycling operations or processes.